Vehicle brake control device

Abstract

A vehicle brake control device cuts off one or more of the first to fourth linear valves in order to prohibit completely supply of a current to the one or more of the first to fourth linear valves, in the case that a slip ratio of one or more wheels is larger than a first threshold. Thus, it is possible to avoid slow depressurization of the W/C pressure caused by the weak current. In other words, it is possible to achieve quick response in the W/C pressures which allows the depressurization to work well.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objective, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings. In the drawings:

FIG. 1 is a diagram showing a hydraulic circuit configuration of a vehicle brake control device according to the first embodiment of the present invention;

FIG. 2 is a block diagram showing input-output relationships of signals of a brake ECU that controls a control system of the vehicle brake control device shown in FIG. 1;

FIG. 3 is a schematic diagram showing operating states of portions in the vehicle brake control device in normal braking and in an abnormal situation;

FIG. 4 is a flowchart showing a brake control process;

FIG. 5 is a timing chart showing changes in current values for the linear valves and W/C pressures;

FIG. 6 is a diagram showing a hydraulic circuit configuration of a vehicle brake control device according to the second embodiment of the present invention;

FIG. 7 is a diagram showing a hydraulic circuit configuration of a vehicle brake control device according to the third embodiment of the present invention;

FIG. 8 is a diagram showing a hydraulic circuit configuration of a vehicle brake control device according to another embodiment of the present invention;

FIG. 9 is a diagram showing a hydraulic circuit configuration of a vehicle brake control device according to still another embodiment of the present invention; and

FIG. 10 is a diagram showing an example of an electrical circuit achieving cutting off the currents to the linear valves.

Claims

1. A vehicle brake control device, comprising: a brake operating member to be operated by a driver;an operation amount sensor for detecting an operation amount of the brake operating member;a first and a second front wheel cylinder, which are respectively installed to two front wheels;a first and a second rear wheel cylinder, which are respectively installed to two rear wheels;a reservoir for storing brake fluid;a main conduit for connecting the first and second front wheel cylinders and the first and second rear wheel cylinders with the reservoir, the main conduit branching into four sections which are respectively connected with the first and second front wheel cylinders and the first and second rear wheel cylinders;a first pump located in a first one of the four sections, the first pump for pressurizing a first one of the first front wheel cylinder, the second front wheel cylinder, the first rear wheel cylinder, and the second rear wheel cylinder by drawing in and discharging the brake fluid stored in the reservoir;a second pump located in a second one of the four sections, the second pump for pressurizing a second one of the first front wheel cylinder, the second front wheel cylinder, the first rear wheel cylinder, and the second rear wheel cylinder by drawing in and discharging the brake fluid stored in the reservoir;a third pump located in a third one of the four sections, the third pump for pressurizing a third one of the first front wheel cylinder, the second front wheel cylinder, the first rear wheel cylinder, and the second rear wheel cylinder by drawing in and discharging the brake fluid stored in the reservoir;a fourth pump located in a fourth one of the four sections, the fourth pump for pressurizing a fourth one of the first front wheel cylinder, the second front wheel cylinder, the first rear wheel cylinder, and the second rear wheel cylinder by drawing in and discharging the brake fluid stored in the reservoir;a first motor for driving the first and second pumps which are provided to a first conduit system of the main conduit and pressurize the first conduit system;a second motor for driving the third and fourth pumps which are provided to a second conduit system of the main conduit and pressurize the second conduit system;first to fourth adjustment conduits, which are located respectively in parallel with the first to fourth pumps and return the brake fluid to the reservoir;first to fourth linear valves, which are respectively located in the first to fourth adjustment conduits; anda control means for controlling, based on a detection signal from the operation amount sensor, the first to fourth linear valves, the first motor, and the second motor,wherein:the control means includes: a first calculating portion for calculating target wheel cylinder pressures corresponding to the operation amount detected by the operation amount sensor when the operation amount sensor detects that the brake operating member is operated;a second calculating portion for calculating slip ratios of the front wheels and the rear wheels; andan adjusting portion for adjusting current values of currents to be supplied to the first to fourth linear valves based on results of calculations of the first and second calculating portions; andthe adjusting portion includes a current cutting means for executing a fist current OFF control when one of the calculated slip ratios is larger than a first threshold value, the first current off control being for cutting off one of the currents for one of the first to fourth linear valves, the one linear valve corresponding to one of the front and rear wheels having the one slip ratio larger than the first threshold value.

2. The vehicle brake control device according to claim 1, wherein: the control means includes a third calculating portion for calculating increase rates of the slip ratios calculated by, the second calculating portion; andthe current cutting means executes a second current OFF control when one of the calculated increase rates is larger than a second threshold value, the second current off control being for cutting off one of the currents for one of the first to fourth linear valves, the one linear valve corresponding to one of the front and rear wheels having the one increase rate larger than the second threshold value.

3. The vehicle brake control device according to claim 1, wherein the adjusting portion performs after executing the first current OFF control: detecting wheel cylinder pressures of the first front wheel cylinder, the second front wheel cylinder, the first rear wheel cylinder, and the second rear wheel cylinder based on detection signals from pressure sensors for detecting respectively the wheel cylinder pressures; andadjusting one of the current values for one of the linear valves which is under control of the first current OFF control, based on one of the detected wheel cylinder pressures corresponding to the one linear valve.

4. The vehicle brake control device according to claim 1, wherein the current cutting means executes the first current OFF control by connecting both ends of the one of the first to fourth liner valves with the ground.